This description relates to high frequency modulation of a light beam in optical recording.
An optical recording system (e.g., an optical disc drive) records data on an optical recording medium (e.g., an optical disc) by writing marks using a laser beam, which is generated by a laser diode in a pickup head. To read data, the laser beam is directed to the recording medium and reflected light is detected to sense the recorded data. The power level of the laser beam is adjusted depending on whether the recording system writing, erasing, or reading data from the disc. A polarizing beam splitter and quarter wave plates are positioned between the laser diode and the disc, configured to allow the laser beam to propagate from the laser diode to the disc and to re-direct the reflected laser beam towards photo detectors.
A small portion of the reflected laser beam may pass through the polarizing beam splitter and reach the laser diode, causing mode-hopping that results in a high level of noise (also called “return feedback noise”), adversely affecting read and write operations. It is known to apply a high-frequency modulation (HFM) current having a fixed frequency and fixed amplitude to the laser diode, causing the laser diode to operate in multi-mode, which is less sensitive to feedback light and has reduced return feedback noise.